The following relates generally to wireless communication and more specifically to frozen bits based pruning and early termination for polar decoding.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system, or a New Radio (NR) system). A wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting wireless communications for multiple communication devices, which may be otherwise known as user equipment (UE).
Wireless communications, however, often involves sending data over a noisy communication channel. To combat noise, a transmitter may encode data in the form of codewords using error correcting codes to introduce redundancy in the codewords so that transmission errors may be detected and/or corrected. Some examples of encoding algorithms with error correcting codes include convolutional codes (CCs), low-density parity-check (LDPC) codes, and polar codes. A polar code is an example of a linear block error correcting code and has been shown to approach the theoretical channel capacity as the code length approaches infinity. For decoding a codeword encoded using a polar code, a receiving device may make a candidate hypothesis of the code length and number of information bits, generate a representation of the information bits using a successive cancellation (SC) or successive cancellation list (SCL) decoding process on the codeword according to the candidate hypothesis, and perform an error checking operation on the representation of the information bits to determine if decoding was successful.
In some cases, the decoding operation may fail because the codeword has experienced excessive corruption (e.g., the codeword was transmitted via a channel with very low signal-to-noise ratio (SNR)), there is no transmitted codeword for the candidate hypothesis (e.g., the codeword represents random noise), the transmitted codeword is intended for a different device, or the candidate hypothesis may be incorrect (e.g., incorrect codeword size, incorrect information bit size, incorrect aggregation level). In some or all of these circumstances, terminating decoding for a candidate hypothesis early (e.g., prior to completion of all decoding processes) may limit power consumption in situations for which the decoding will be unsuccessful. However, differentiating circumstances in which early termination is appropriate (e.g., without terminating decoding early for some decoding processes that could have been successful) provides challenges for existing implementations. Other known techniques for facilitating early termination increase decoding complexity, decreasing the benefits provided by early termination.